Wooden boxes, drawers and storage chests and a variety of other wooden furniture and other objects often use dovetail joints as a means of securely assembling components. A dovetail is a joint, usually right angled, formed of one or more projecting parts, i.e., tenons or pins, that fit tightly within corresponding recesses, i.e., mortises or gaps between tails, to form a joint. The pin is typically broader at its end than at its base. Dovetail joints are considered by most cabinet makers to be the strongest and most permanent joint typically made in cabinet making. A dovetail joint is generally employed in articles made of thinner materials such as drawers, boxes, chests, and the like.
Dovetails are used for both their decorative appearance and their high strength. Such joints can be made without industrial machinery in one of two principal ways, either using hand tools: saws and chisels, or using power tools such as a router. In both cases, making such a joint requires a high degree of skill and precision. Furthermore, making such a joint using hand tools is time consuming. The desire to save time motivates some woodworkers to use power tools, and the need for precision, often in the relative absence of skill, makes jigs or machines that control the power tools desirable.
The use of a power tool such as a router allows two different approaches. The router can be held stationary and the workpiece moved relative to the position of the router cutter, or the workpiece can be held stationary and the router moved relative to the workpiece. Additionally, in a variation of both basic approaches, both the router and the workpiece may move.
The modern electric router has made this process much easier with the help of router cutters, holding fixtures and templates. With fixtures, the workpiece is clamped into the fixtures and machined after the template location is set.
Most dovetail and other joint-making jigs utilize an array of “fingers” to guide a router cutter during engagement of the workpiece or workpieces to remove waste material and leave “pins” on one work piece and “tails” on the other work piece. The arrays of fingers are typically provided in one of two ways. In the first alternative template structure, a molded or machined plastic or metal template has multiple fingers, each of which has a fixed position relative to other fingers on the template. In the second alternative, fingers are attached to and can be moved relative to each other on a finger-carrying plate or bar, which facilitates manufacture of joints with variably spaced pins and tails rather than ones that are spaced only the predetermined amounts required by a molded or machined template.
One of the challenges associated with use of joint-making jigs is adjustment of joint fit. Because of differences in wood species, cutter geometry and diameter and other reasons, it is desirable to be able to adjust the exact path of the router cutter. This is sometimes done by making possible adjustment of the finger-carrying template plate or bar (and, therefore, finger positions) in setting up the jig or in the course of use or both.